Usefulness of a Z-score of E' versus raw E' velocities to detect left ventricular dysfunction in patients with mitral or aortic regurgitation or dilated cardiomyopathy.

Despite their potential as a sensitive measure of ventricular performance, tissue Doppler velocities vary with normal aging. This is inconvenient for nonspecialists to interpret and makes it difficult to use as an entry criterion for clinical studies. The age-adjusted tissue Doppler Z-scores might avoid these disadvantages and be more discriminant for myocardial impairment than the raw velocities. We conducted a meta-regression of studies reporting age-specific normal tissue Doppler velocities to determine a consensus formula for Z-scores (8 studies, 1,867 patients) that we then tested in an independent study at our institution. We next compared the Z-scores head-to-head with the raw velocities for their ability to distinguish a fresh set of 81 healthy subjects from groups in whom subtle ventricular dysfunction might be expected, including 50 patients with dilated cardiomyopathy, 50 with aortic regurgitation, and 50 with mitral regurgitation. The discriminant capacity, assessed by the area under the receiver operating characteristic curves, was higher for the Z-scores than for the raw velocities in each patient group. At the septal angle of the mitral annulus: dilated cardiomyopathy 0.95 versus 0.92 (p = 0.03), aortic regurgitation 0.83 versus 0.78 (p = 0.02), mitral regurgitation 0.85 versus 0.81 (p = 0.04). At the lateral angle: dilated cardiomyopathy 0.94 versus 0.88 (p = 0.005), aortic regurgitation 0.92 versus 0.83 (p = 0.001), mitral regurgitation 0.87 versus 0.85 (p = 0.31). In conclusion, the Z-scores of the tissue Doppler velocities were better than the raw velocities at detecting myocardial impairment in valvular or heart muscle disease. The calculation needs only the raw velocity and patient age. Tissue Doppler Z-scores could be used to create a novel, more sensitive, definition of ventricular dysfunction and might make it easier for nonspecialists to interpret the reports.